Blocking-resistant plasticizer articles,compositions and processes

ABSTRACT

THIS DISCLOSURE IS DIRECTED TO (1) BLOCKING-RESISTANT, PARTICULATE, TACKIFYING PLASTICIZER DOLIDS, EACH HAVING A RANDOMLY-SHAPED SOLIC DORE OF TACKIFYING PLASTICIZER, AND A SUBSTANTIALLY CONTINUOUS, SOLID-RETIAINING, COMPARATIVELY HARD COVERING OF HIGHER MELTING POLYMERIC MATERIAL; (2) HEAT-ACTIVATABLE PLASTICIZED THERMOPLASTIC ADHESIVES CONTAINING A PROFUSION OF INDIVIDUALLY COVERED PLASTICIZER SOLIDS DISTRIBUTED UNIFORMLY THEREIN; (3) ARTICLES OF MANUFACTURE, E.G., PREPASTED WALLPAPER AND WALL COVERINGS, CONTAINING SAID ADHESIVE COATED, IMPREGNATED, JOINED, SECURED, OR OTHER WISE APPLIED TO A SUITABLE SUBSTRATE MATERIAL, E.G., CONVENTIONAL WLLPAPER BASE STOCK (PREFILLED OR UNFILLED), CONVENTIONAL WASHABLE WALL COVERING MATERIAL (PLASTICIZED) POLYVINYL CHLORIDE DEPOSITED ON AND/OR INTO THE VIEWED SIDE OF THE CLOTH); (4) PROCESSES FOR MAKING THE BLOCKING-RESISTANT, PARTICULATE, TACKIFYING PLASTICIZER SOLIDS; (5) PROCESSES FOR MAKING ARTICLES (3); (6) PROCESSES FOR APPLYING PREPASTED ARTICLES (3) TO A BASES(S), E.G., WALLS OF PLASTER, CONVENTIONAL GYPSUM DRY-WALL, WOOD, ETC.; AND (7) COMPOSITE ARTICLES OF MANUFACTURE COMPRISING A BASE TO BE COVERED, DECORATED, PROTECTED, ETC., WITH THE ARTICLES (3) ADHERED OR OTHERWISE SECURED THERETO, E.G., PREWALLPAPERED DECORATIVE PANELLING WHERE THE WALLPAPER ON THE ADJACENT BASE PANELS IS PREMATCHED, PERMANENT OR SEMIPERMANENT RECORDS, E.G., COMPRISED OF PAPER CONTAINING PRINTED MATTER OR INDICIA WHICH IS PRESERVED BY LAMINATION WITH A PROTECTIVE FILM, LAYER OR SHEET USING THE HEAT SEALABLE ADHESIVE (2) AS THE LAMINANT.

United States Patent 3,558,418 BLOCKING-RESISTANT PLASTICIZER ARTICLES,COMPOSITIONS AND PROCESSES Erland C. Porter, Jr., Dayton, Ohio, and HansF. Huber,

Wiesloch, Germany, assignors to The National Cash Register Company,Dayton, Ohio, a corporation of Maryland No Drawing. Filed May 22, 1968,Ser. No. 731,265 Int. Cl. B32b /16, 5/30 US. Cl. 161-162 24 ClaimsABSTRACT OF THE DISCLOSURE This disclosure is directed to (l)blocking-resistant, particulate, tackifying plasticizer solids, eachhaving a randomly-shaped solid core of tackifying plasticizer, and asubstantially continuous, solid-retaining, comparatively hard coveringof higher melting polymeric material; (2) heat-activatable plasticizedthermoplastic adhesives containing a profusion of individually coveredplasticizer solids distributed uniformly therein; (3) articles ofmanufacture, e.g., prepasted wallpaper and wall coverings, containingsaid adhesive coated, impregnated, joined, secured, or otherwise appliedto a suitable substrate material, e.g., conventional wallpaper basestock (prefilled or unfilled), conventional washable wall coveringmaterial (plasticized polyvinyl chloride deposited on and/or into theviewed side of the cloth); (4) processes for making theblocking-resistant, particulate, tackifying plasticizer solids; (5)processes for making articles (3); (6) processes for applying prepastedarticles (3) to a base(s), e.g., walls of plaster, conventional gypsumdry-wall, wood, etc.; and (7) composite articles of manufacturecomprising a base to be covered, decorated, protected, etc., With thearticles (3) adhered or otherwise secured thereto, e.g., prewallpapereddecorative panelling where the wallpaper on the adjacent base panels isprematched, permanent or semipermanent records, e.g., comprised of papercontaining printed matter or indicia which is preserved by laminationwith a protective film, layer or sheet using the heat sealable adhesive(2) as the laminant.

While a representative concentration of the plasticizer solids (1) areof random shape, the predominant shape is generally spherical asobserved through the electron microscope at magnifications of 48,000+times. Each covered plasticizer particle (1) was observed to have acontinuous bumpy covering ranging in thickness from about 0.02 to about20 microns. The bumps or protuberances (surface projections of generalrounded shape) appeared as a part of the covering and ranged in sizefrom about 0.01 to about 1.0 micron with the thicker coverings havingthe larger bumps and vice versa, as gleaned from electronphotomicrographs. 4

The substantially continuous covering is comprised of polymeric materialhaving a melting range, the threshold temperature of which is higherthan the melting range (thermal activation temperature) of saidtackifying plasticizer, said tackifying plasticizer solids characterizedby being in a nontacky, blocking-resistant form at ambient temperaturesdue to inhibition of the cold-flowing tendency provided by saidcontinuous covering. Hence, each individual plasticizer particle (core)has its own continuous covering. The thermoplastic adhesives (2) areheatsealable, thermoplastic adhesive compositions which are renderednontacky and resistant to blocking at ambient temperatures due to thepresence of a profusion of uniformly distributed continuously coveredplasticizer solids (1) described above.

Since the covering material has a melting range, the

threshold temperature at which the covering material begins to melt) ofwhich is higher than the thermal activation temperature of thethermoplastic adhesive; the tackifying plasticizer core melts and isable to egress through the liquid-porous covering upon thermalactivation of said adhesive composition (viz, the thermoplastic adhesiveand the tackifying plasticizer), thereby uniformly imparting increasedtack to said adhesive. At temperatures below thermal activationtemperature the covering restricts access of the solid plasticizer coresto the thermoplastic adhesive matrix because the covering issolids-retaining. This inhibits the cold-flowing tendency of saidtackifying plasticizer solids and preserves a nontacky,blocking-resistant condition at most ambient room and storagetemperatures.

Another advantage attendant to the adhesives of this invention is thatthey are readily strippable, viz, the thermoplastic adhesives can bemobilized thus allowing moving or removal of the substrate due to theheat liquefying the adhesive bond. Hence, when the adhesive areprepasted on wall covering, e.g., wallpaper, substrates; the productsare prepasted thermally strippable wall coverings. Since heat is theagency used to place the adhesive in strippable condition, the strippingoperation is neat, efficient, inexpensive and saves considerable timecompared to the laborious Wetting and scraping removal technique usedwith conventional wallpapers and coverings. The same device used toactivate the adhesive thermally and apply the wallpaper substrate can beused to strip the substrate; and, in general, the same temperaturesprevail for stripping as for application.

Heat sealing thermoplastic adhesive compositions have enjoyed widespreadusage. Such compositions are usually comprised of one or more compatiblethermoplastic resins with one, or a mixture of, plasticizer(s), andoptional adjuvant materials such as fillers, coloring agents, etc., toassist in tailor-making the adhesives to suit specific end uses.Plasticizers are employed in the thermoplastic heat sealing compositionsto increase their tackiness so as to enable adhesive films to attaintheir full adhesive power when the heat is applied to them.

The inclusion of plasticizers in the thermoplastic adhesives has createdcertain problems, however. One of the problems is that the plasticizerswhich are frequently best with respect to increasing the tackifyingproperties of these heat sealable thermoplastic adhesives films, alsounfortunately tend to be very cold-flowable, viz, these plasticizerstend to flow or migrate through the plastic film at ambient roomtemperature and storage conditions. This cold-flowing in turn results inpremature local activation or an increase in surface tackiness of thethermoplastic films. This undesirable plasticizer migration causes thefilms to block or adhere to one another or the substrates upon which thefilm is deposited, e.g., when a plurality of thermoplasticadhesive-coated substrate sheets are stacked one upon another, or whenthe adhesive coated substrate is rolled, e.g., as occurs in rolls ofcoated (prepasted) wallpaper, plastic wall covering, plastic film, etc.The problem of blocking or premature activation of the thermoplasticadhesives is an expensive one, since it occurs most frequently afterpreparation of the final coated article has occurred, e.g., duringstorage thereof but prior to use, e.g., application of thethermoplastic-coated substrate to the base for which it is intended.Consequently, the blocking problem has led to the wasteful and expensivediscarding of large amounts of thermoplastic-coated substrate materials.

One possible solution to this problem is to significantly reduce theamount of plasticizer incorporated into the heat sealable thermoplasticadhesive composition. This approach is not really feasible, however,since the adhesive then possesses less than the desired extent ofadhesive power to join the substrate (upon which it is deposited) to thebase to which the substrate is to be adhered. Hence, the development ofa thermoplastic adhesive having balanced properties of strong adhesivepower combined with good resistance to blocking at ambient roomtransportation and storage temperatures has long been desired.

Another attempted prior art solution to the problem of blocking inthermoplastic heat sealable adhesive compositions is the approachcontained in US. Pat. 2,613,191. This approach renders thermoplasticheat scalable compositions resistant to blocking by formation of solidmatrices of polyvinyl alcohol or similar emulsifying agent about solidparticles of plasticizer, the polyvinyl alcohol providing amatrix-coating in which the solidified plasticizer particles arerestrictively contained. Then upon heating the thermoplastic adhesive toits thermal activation temperature, the polyvinyl alcohol matrix(containing many solid plasticizer particles) melts to assist inrendering the thermoplastic adhesive tacky. When the approach in US.Pat. 2,613,191 does render the plasticized thermoplastic adhesiveresistant to blocking; the restricted spatial access of the individualsolidified plasticizer particles to the thermoplastic adhesive detractssomewhat from the overall adhesive power probably due to the fact that aplurality of plasticizer particles are present in each polyvinyl alcoholmatrix.

The present invention constitutes a marked improvement in thermoplasticheat-scalable adhesives because it enables the attainment ofthermoplastic adhesive compositions which are not only highly resistantto blocking at ambient temperatures, but also possess strong adhesivepower upon thermal activation thereof.

The present invention, by providing each plasticizer solid particle as acore with its own adherent covering spatially separates each of thenormally cold-fiowable tackifying plasticizer solids from thesurrounding matrix of thermoplastic adhesive thereby inhibiting theblocking which results from cold flow at ambient temperature conditions.Since the covering is very thin, however, the restriction to access ofthe plasticizer to the thermoplastic resins does not detractsignificantly from the adhesive power of the adhesive upon thermalactivation thereof. In other Words each covering has the effect ofretaining its plasticizer core from migratory cold flow movement atambient temperature conditions, but upon thermal activation of thethermoplastic adhesive, the plasticizer core melts and then migratesuniformly throughout the thermoplastic adhesive since it has the abilityto readily egress from the previously restrictive covering. Since thepolymeric material of which the covering is comprised has a highermelting point than that of both the plasticizer particles and thethermoplastic resin(s); the coverings for each plasticizer core canremain as solids upon thermal activation of the thermoplastic adhesive.Of course, it is also within the purview of this invention to formulatethe covering of materials which will also melt during thermal activationof the thermoplastic resin(s). In such cases, the covering then becomesa portion of the total thermoplastic adhesive, e.g., as a filler,adhesive component, etc., upon thermal activation of the adhesive.

The present invention constitutes a marked departure from the approachof US. Pat. 2,613,191. As noted above, said patent envelops manyindividual solid plasticizer particles (cores) within each polyvinylalcohol localized matrix with said matrices being enveloped in turn bythe thermoplastic resin matrix. According to the present invention aseparate continuous covering is secured about each individualplasticizer particle (core), thereby allowing more uniform distributionof said plasticizer particles in, and greater access to, the matrix ofthermoplastic resin during thermal activation of the adhesive.Comparatively speaking, the structure involved in the plasticizedthermoplastic adhesive of US. Pat. 2,613,- 191 involves a double matrix,viz, many, individual solid particlulate plasticizer particulate corescoated or enveloped completely in each matrix of polyvinyl alcohol, withmany of such matrices being present in the overall thermoplasticadhesive matrix.

PLASTICIZERS While a single highly tackifying plasticizer can beemployed, frequently it is desirable to employ more than one plasticizerto attain the tailor-made plasticizing properties desired for a giventhermoplastic heat sealable adhesive. Thus, in accordance with thisinvention, one or more or all of such plasticizers can be provided withliquid-porous, solid-retaining coverings. Frequently, in the combinedinterests of economy and to enhance the adhesive power of giventhermoplastic adhesive compositions, it is desirable to provide only theplasticizer(s) having the greater and more problematic cold flowingtendencies with the individual coverings. Any plasticizer can beemployed which enhances the adhesive power during the thermal activationof the thermoplastic adhesive so long as the plasticizer is a solid atambient temperatures and for all practical purposes substantiallyinsoluble in water. The expression ambient temperatures as used hereinis with reference to temperatures approximating those normally found inrooms in buildings, storage facilities, and transportation facilities inmoderate to Warm climates. Of course plasticizers can also be employedwhich are solids at such temperatures and temperatures below them. Ofcourse, individual plasticizers have different melting points (or morerealistically speaking melting ranges), and the lower meltingplasticizers can be rendered blocking resistant by the present inventionat storage and transportation temperatures which are normallyencountered in moderate climates, viz, temperatures up to about F.; yetthese plasticizers may bleed somewhat in warm to very warm climates.Nevertheless, the present invention enhances the resistance of suchplasticizers to blocking compared to compositions wherein the solidplasticizer particles are not individually or otherwise covered.

Suitable plasticizers which are both water-insoluble and solid atambient temperatures and which can be employed in accordance with thisinvention include, but are not limited to, the following: hydroabietylalcohol, triethylene glycol dibenzoate; benzophenone; chlorinatedbiphenyls; chlorinated polphenyls, e.g., those having specific gravitiesat 25 C. ranging from about 1.670 to 1.734; mixtures of meta and paraterphenyls, e.g., such as the commercially available plasticizermixtures sold by Monsanto Company under the trade designation Santowax M& P; aryl sulfonamide-formaldehyde resin plasticizers, e.g., thecommercially available Santolite MHP plasticizer of Monsanto Company;tricyclohexyl citrate; diphenoxyethyl fumarate; 2-butoxyethylpelargonate; triphenyl phosphate; tri(p-tertiary butyl)phenyl phosphate;tri(dichloro)phenyl phosphate; dihexyl phthalate (nand iso-);dihydrobiethyl phthalate; dicyclohexyl phthalate; diphenyl phthalate;diethoxyethyl phthalate; 1,2-propylene glycol monostearate; glycolmonostearate; diethylene glycol distearate; tetraethylene glycolmonostearate; tetraethylene glycol distearate; sucrose octaacetate;orthoand para-toluene sulfonamides; N-ethyl para-toluene sulfonamides;N-cyclohexyl para-toluene sulfonamides; diphenyl phosphate; indene resinplasticizers, e.g., those materials commercially available under thetrade designation Neoindine R3; rosin ester plasticizers, e.g., thecommercially available glycol ester of rosin acid referred to by thetrade designation Staybelite Ester Number 10; terpene-phenolic resinplasticizers, e.g., those commercially available materials referred toby the trade designations SP 533 and SP 560; polystyrene plasticizingresins having specific gravities at 25 C. ranging from about 1.02 to1.07 and having melting points of about 30 C. and higher, e.g., thecommercially available Piccolastic and Piccotex polystyreneplasticizers, etc. Further information concerning the physicalproperties and compatibility of the above mentioned plasticizers withconventionally employed, commercially available thermoplastic resins canbe found in the article entitled Plasticizers by J. T. Freeze (1965).Modern Plastics Encyclopedia, pages 352 to 380, the disclosure of saidarticle being incorporated herein by reference. It will be observed thatthe above-mentioned suitable exemplary plasticizers represent a widevariety of chemical categories. This should illustrate the fact that solong as the plasticizer material is substantially insoluble in water (soas to enable the individual covering to be applied thereto) and has amelting point sutficiently high to enable it to maintain its solidity atthe ambient temperatures encountered, such plasticizer(s) can beprovided with individual coverings to enhance their resistance toblocking. Of course, in any given thermoplastic adhesive compositions aplasticizer(s) will usually be employed which is substantiallycompatible with the thermoplastic resin(s) with which it is to beemployed. Hence, the parameters for determining suitability of anygiven, specific plasticizer are more oriented toward certain of itsphysical properties than toward the chemical family to which thematerial belongs.

Since, as noted above, a plurality of plasticizers can be, and oftenare, used to render the thermoplastic resin(s) adhesive and tacky at thethermal activation temperatures; it is within the purview of thisinvention to employ comparatively minor amounts of a plasticizer whichis partially incompatible with the thermoplastic resin adhesive so longas the composite plasticizer exhibits adequate compatibility. In otherwords, minor amounts of a comparatively incompatible plasticizer(s) canbe used in combination with another resin-compatible plasticizer(s), theimportant thing being that the composite plasticizer behavior being oneof compatibility with the thermoplastic resin adhesive.

INDIVIDUAL COVERING MATERIALS The polymeric material employed to formthe covering must have a melting point, the threshold temperature ofwhich is higher than the melting range of both the thermoplastic resinadhesive(s), which constitute the predominate portion of theheat-scalable adhesive formulation, and the selected plasticizer(s)which imparts to said ad- 'hesive its tackifying properties at thetemperatures of thermal activation. Any polymer material which iswaterinsoluble and has a higher threshold melting temperature than boththe plasticizer and thermoplastic adhesive can be used as the coveringmaterial so long as it is capable of coagulation about the solidplasticizer core particles. For example, latex and/or resin emulsionscontaining the polymer(s) in particulate solid form so as to enable themto be coagulated, precipitated or otherwise deposited upon theplasticizer core particles are used. These latices are deposited byheated, addition of precipitating ions (salts), addition of nonsolvents,or a combination thereof.

The term threshold temperature as used herein is intended to indicatethe lower temperature at which the thermoplastic adhesive andplasticizer(s) begins to melt within its melting range. The term meltingrange is intended to have its usual meaning, viz, the range oftemperatures over which the room temperature solid thermoplasticadhesive and plasticizer(s) change from solids to liquids, viz, thetemperature range over which they melt.

Suitable water-insoluble, polymeric covering materials which can beemployed in accordance with this invention include, but are not limitedto, the following water-insoluble polymers and resins: polyvinyl acetatehomopolymers and copolymers, e.g., copolymers containing a major amountof vinyl acetate with a minor amount of methyl or ethyl acrylate;polyvinyl chloride homopolymers and copolymers, e.g., copolymerscontaining the same or a major amount of vinyl chloride with the same ora minor amount of vinyl acetate; copolymers of alkyl esters ofdicarboxylic acids, e.g., dibutyl maleate, with vinyl monomers, e.g.,vinyl acetate; acetoxylated polyalkylenes, e.g.,

copolymers of ethylene, propylene, butenes with vinyl acetate; vinylchloride-alkyl acrylate copolymers, e.g., with C to C alkyl acrylate andmethacrylates, such as, methyl acrylate, ethyl acrylate, methylmethacrylate; vinyl acrylate homopolymers; copolymers of acrylic acidwith olefinically unsaturated monomers, e.g., butadiene-1,3; vinylchloride; polyvinyl butyral; polyvinylidene chloride; copolymers ofvinylidene chloride; copolymers of vinylidene chloride with acrylicacid, acrylonitrile, methyl acrylate, ethyl acrylate, etc.; homopolymersand copolymers of vinyl stearate, vinyl pyridine, vinyl styrene,styrene, methyl styrene, cyanoacrylate; polyethylene, polypropylenes,ethylene-propylene copolymers; ethylene-propylene terpolymers, e.g.,terpolymers of ethylene, propylene and a conjugated or nonconjugated Cto C diene, e.g., hexadicue-1,3, hexadiene-l,4, etc.; copolymers ofstyrene with butadiene and/or acrylonitrile; natural rubber;polychloroprene rubbers, e.g., polychloroprene, copolymers ofchloroprene and acrylonitrile; natural rubber; butyl rubber (copolymersof isobutylene and small amounts of diolefins, e.g., isoprene;carboxy-modified copolymers of butadiene and acrylonitrile; etc.

In order to obtain the full measure of the benefits available by thepresent invention, it is necessary to employ the plasticizer (covered)and covering material in certain weight ratios. Accordingly, the weightratio of the covered plasticizer to the covering material can range fromabout 1.5 to 20:1. At weight ratios below about 1.5 :1 adhesion of thethermoplastic resin adhesive sufiers when the plasticizer(s) areincorporated in the normally employed concentration ranges with respectto the thermoplastic resin adhesive. On the other hand, at weight ratiosof plasticizer to covering material in excess of about 20: 1, heavyblocking, spotting and fiber picking occurs. The latter problem isespecially acute when thermoplastic resin adhesives containing thecovered plasticizers wherein the weight ratio of plasticizer to coveringmaterial exceeds 20:1 is employed in conjunction with an unsized andhence highly porous fibrous substrate, e.g., unsized wallpaper basestock. Usually weight ratios of said plasticizer to covering material ofgreater than about 1.7 :1 to approximately 12:1 are used, With thepreferable weight ratios of the plasticizer to the covering materialvarying from approximately 1.8:1 to 12: 1, especially when fibroussubstrates, e.g., comparatively nonporous paper substrates are employedin conjunction therewith. An example of a comparatively nonporous papersubstrate is commercially available prefilled wallpaper stock.

While the average thickness of the covering can range from about 0. 02to about 20 microns, usually it ranges from about 0.05 to about 10microns and more usually from about 0.1 micron to about 10 microns.

It should be noted however that the thickness of the individual coveringcan exceed 20 microns in cases where the covering material is to beheated at temperatures in excess of the threshold of its melting rangeduring thermal activation of the adhesive. In such cases practically anycovering thickness can be used which is consumate with adequate adhesivepower.

When the covered individual tackifying plasticizer cores are heated to atemperature in excess of their melting range, microscopic studies revealthat the core material, viz, the tackifying plasticizer, egresses fromthe covering with the result that large sections of the covering areoften ruptured, e.g., in certain portions; and the plasticizer thusegresses from the covering. In other cases, small portions of thecovering are ruptured, ostensibly breaking the covering structure intosmall individual or agglomerate portions. Actually, a mixed behavior isobserved during egress with the melted plasticizer in some casesbreaking through certain portions of the covering as it leaves and inother cases the droplets of melting plasticizer simply appear to passthrough the liquid covering leaving the predominant portion of itostensibly unruptured. In this re- 7 spect the substantially continuouscovering appears to be liquid porous.

THERMOPLASTIC RESIN (S) A wide variety of thermoplastic resins can beemployed to constitute the predominate portion of the heat activatable,thermoplastic adhesive formulations on a weight basis. Not only one buta mixture of various thermoplastic resins can be used. The selection ofa given thermoplastic resin or mixture thereof will be dictated largelyby the properties desired in the final adhesive, e.g., thermalactivation temperature, viz, the heat sealing temperature or temperaturerange desired for a given application; adhesive power for a givensubstrate; etc. Bearing this in mind, suitable thermoplastic resinswhich can be employed in accordance with this invention include, but arenot limited to, the following: cellulose acetate; cellulose acetatebutyrate; cellulose nitrate; ethyl cellulose; polymethyl methacrylate;polystyrene; polyvinyl acetate; polyvinyl chloride; copolymers of vinylchloride and vinyl acetate, e.g., those containing from about to 88percent vinyl chloride and 80 to 12 weight percent vinyl acetate;polyvinyl butyral (polyvinyl butyraldehyde); polyvinylidene chloridehomopolymers and copolymers; nondrying alkyd resins; nondrying phenolicresins; coumarone-indene resins; mixtures containing any two or more ofthe aforementioned materials; etc. Thus it will be realized that a widevariety of different types of natural and synthetic thermoplastic resinscan be employed in accordance with the present invention. Of course, tosuit a given specific purpose for which the heat sealing adhesive is tobe employed, a given particular thermoplastic resin or mixture thereofcan be selected which incorporates nonthermoplastic components.

ADHESIVE COMPONENTS The adhesive compositions of this invention usuallycontain a thermoplastic resin(s), a plasticizer(s) at least a portion ofwhich is solid particulate with individual coverings and optionalcoloring agents, fillers, stabilizers, etc., with the optionalformulation agents being present in conventional concentrations for heatscalable thermoplastic compositions.

According to one of the embodiments of the present invention, aplurality of plasticizers is employed with one or more but usually notall of the plasticizers being covered. Accordingly, the concentration oftotal plasticizer, based on total adhesive, can range from about 19.0 toabout 33.3 weight percent, usually ranges from 21 to 29 weight percent,and more preferably (especially for wallpaper end use applications)ranges from 22 to about 25 weight percent. The concentration ofindividually covered particulate plasticizer, based on totalthermoplastic adhesive including plasticizers, can range from about 7.0to about 25.0 weight percent, usually ranges from about 7.3 to about17.5 weight percent and preferably ranges from about 7.5 to about 10.0weight percent. The concentration of uncovered plasticizer, viz,plasticizer which is in direct contact with the thermoplastic resinadhesive, can range from about 0 percent to about 17.5 weight percent,usually ranges from about 7.1 to about 17.1 weight percent andpreferably ranges from about 7.3 to about 16.7 weight percent expressedas a weight percent based on total adhesive.

The concentration of higher melting polymer, including that providingthe individual covering, based on total adhesive, can range from about0.3 to about 18 weight percent and preferably ranges from about 8.3 toabout 10.8 weight percent.

A wide variety of porous and nonporous materials can be employed assubstrates in accordance with this invention. Of course, the particularsubstrate employed is in accord with the predetermined end use for whichthe article (3) is to be employed. Suitable exemplary substrates whichcan be employed include, but are not limited to, the following: porousand comparatively nonporous paper, e.g., wallpaper stock which ranges inweight from about 40 to about pounds per 3000 ft. ream (both filled andunfilled) various metal foil materials, such as aluminum foil, tin foil,copper foil, gold foil, etc.; various plastic film, sheet and layermaterials, such as polyester, e.g., polyethylene glycol terephthalate(Mylar), polyvinyl chloride, polyvinyl acetate, copolymers of vinylchloride and vinyl acetate, polyethylene, polypropylene, copolymers ofethylene and propylene, terpolymers of ethylene, propylene andconjugated or nonconjugated C to C diolefins; woven or nonwoven fabrics,e.g., cotton, polyamides, e.g., nylon, glass fibers, polyester fibers,e.g., Dacron, acrylic fibers, e.g., Acrylan; washable wall coverings,e.g., cloth coated with flexible water resistant plastic materials,e.g., plasticized polyvinyl chloride, using a plasticizer such asdibutyl phthalate, dioctyl phthalate, di-2-ethyl hexyl phthalate, etc.

The amount of adhesive employed, based on area of substrate covered(expressed as pounds per 3000 ft. ream), can vary widely depending uponthe end use of the ultimate article, method of application of thecoating, viscosity of the coating composition, substrate porosity, andother factors. Hence, the amount of the thermoplastic adhesive applied,based on substrate area, can range from about 1 to about 50 pounds per3000 ft. ream. Usually, however, for most purposes the adhesive rangesfrom about 4 to about 40 pounds per ream and in the case of wallpaper,aluminum foil, Mylar and vinyl plastics, the concentration of totalthermoplastic adhesive ranges from about 5 to about 30 pounds per ream.

FORMATION OF INDIVIDUALLY COVERED PLASTICIZERS SOLIDS The individuallycovered plasticizer solids of this invention can be prepared readily bydispersing the solid plasticizer(s) particles, which are usuallypreviously ground to a particle size of less than about 50 microns, infinely ground form in a latex of a comparatively hard, higher melting,water-insoluble polymeric material. The polymer latex particles usuallyrange in average size from about 0.5 to about 2 microns. The dispersionmedium for the latex is usually water. While this aqueous dispersion,viz, aqueous latex, is being agitated, a precipitating agent such as asalt, e.g., monosodium phosphate, is added. This alfects precipitationor coalescence of the polymeric latex particles. Coalescence can also besecured by heating.

As the polymeric latex particles coalesce, they accumulate about thedispersed solid plasticizer particles thus depositing thereon thin,individual coverings of the comparatively hard, higher melting coveringpolymer. Upon completion of the latex precipitation each of theindividual, solid plasticizer core particles is provided with a thin,solid-retaining, liquid-porous, substantially continuous covering of theharder, higher melting polymer. This covering acts as an effectivebarrier against premature mixing in the solid state of the plasticizerwith the thermoplastic resin, which solid state mixing, viz, cold flow,results in blocking. Electron microscope studies (at magnifications of48,200; 79,000; 110,000 and 142,000zto one) reveal the coverings to besubstantially continuous in that no openings are observable therein.

Subsequent to formation of the covering, the covering is aged. Thisageing" is conducted by heating the covered plasticizer particles attemperatures ranging from about 40 C. to a practical maximum temperaturebelow the melting range of the core plasticizer, usually about 55 C.,for time periods ranging from about 10 to about 300 minutes. One effectof the ageing is to increase the adhesion of the higher melting polymerparticles to the core of tackifying plasticizer(s) Upon melting thecore, such as occurs during thermal activation of the adhesive, thetackifying plasticizer material readily egresses, viz, flows out of thecovering. Thus, upon application of heat, the adhesive, containing theindividually covered tackifying plasticizers solids, is activated; yetthe blocking resistance of such compositions is greater than that whichprevails when the same tackifying plasticizer solids are not providedwith such individual coverings. Moreover, the adhesive performance ofheat scalable thermoplastic resin adhesive compositions containing theindividually covered plasticizer solids is superior to that ofcompositions containing the same amount of the tackifying plasticizer(uncovered) and an equivalent amount of the extending, viz, highermelting covering material, viz, latex.

The thermoplastic adhesives containing a profusion of uniformlydistributed individually covered tackifying plasticizer solids areusually applied as aqueous dispersions containing from about 30 to about60 percent, by weight, adhesive solids and can be prepared readily fromthe aged individually covered plasticizer solids by the followingillustrative exemplary procedure: 54.5 parts of 55 percent Borden Polyco2188 emulsion and 127 parts of 55-percent Borden Polyco 2190 emulsionare added to a suitable vessel equipped with a stirrer. To this emulsionblend is added, with stirring, 65 parts of an aqueous SE dispersionwhich contains 50 percent solids (30.0 parts SE10 covered individuallywith 2.5 parts Borden Polyco 2188 particles) (12:1 phase ratio). Alsoadded with stirring is 140 parts of a DPP-MHP aqueous dispersion whichcontains 50 percent solids (60 parts DPP, 10 parts MHP, and aconventional small amount of Tamol-731 which is used as the dispersingagent). 18.5 parts of water are then added to adjust the total solids ofthe formulation to approximately 50 percent.

, The articles of manufacture referred to herein by the designation (3)and comprising the thermoplastic adhesives (2) joined to a paper orother substrate can be prepared readily in accordance with thisinvention by knife coating, roller coating, spraying, depositing, orotherwise joining, the adhesive (2) to the desired substrate. Anexemplary, illustrative procedure for preparing the articles ofmanufacture (3) is as follows: In order to reduce the amount of coatingweight of the thermoplastic adhesive formulation necessary, a fillercoating is first applied to the wallpaper base stock. The filler coatingconsists of 2 parts of a suitable clay, and, one part of a suitablelatex, e.g., Polyco 2186, Dow SBR (styrenebutadiene rubber) latex,dispersed in 2 parts Water containing a dispersing agent such as Calgon.This is a conventional filler coating formulation used throughout thepaper and coating industry.

An approximately 10 pounds/ 3000 sq. ft. ream coating is applied to an18 oz. (approximately 60 pounds/3000 sq. ft. ream) paper by means ofconventional coating techniques (i.e., air-knife coater, puddle-bladecoater, gravure roll, trailing-blade coater, reverseroll coater, etc)?This coating is then dried by conventional techniques, i.e., a forcedair drying tunnel with three temperature zones. The air flow rate can beadjusted separately in each of the three temperature zones. Thetemperatures in the three zones can also be varied. This fillerf coatedwallpaper stock can then be rewound for later use.

The filled wallpaper stock is then coated With from 10 pounds/ 3000 sq.ft. ream to 20 pound/3000 sq. ft. ream of the thermoplastic adhesivecomposition of this invention by conventional coating techniques asindicated above. The drying procedure can be the same as used in thecase of the filler coating. It is important in this step that thetemperature of the paper web being dried does not exceed the thermalactivation temperature of the thermoplastic adhesive formulation becausepremature activation leads to blocking and picking when the coated rollis unwound later for printing. It must be noted, however, that thetemperature of the air in the first zone may be considerably higher thanthe activation temperature. This is compensated for by the water whichis leaving 10 the web so that the actual temperature of the web is stillbelow the thermal activation temperature.

It is also possible to coat the filler coating and the thermoplasticadhesive formulation on a single pass through the coating apparatus. Thefiller" coating is first applied by conventional techniques, andpartially dried as above. The web then continues to a second stationwhere the thermoplastic adhesive composition is coated via conventionaltechniques and the web is then further dried to 5 percent moisture inthe three zone drying tunnel. It is then wound on a core ready to beprinted.

It should be clearly understood that it is within the purview of thepresent invention to provide the noncoated side of the substrate, e.g.,paper, with a design, printing, embossment, or other monoorpolychromatic indicia. Thus, for example, 55 to pounds per 3000 sq. ft.ream wallpaper base stock can be provided with a multicolored designprior to the deposition of the thermoplastic adhesive formulationcontaining the discontinuously covered plasticizer solids thereon. Also,it is possible in accordance with this invention to first apply thethermoplastic adhesive formulation containing the discontinuouslycovered plasticizer solids uniformly distributed therethrough to oneside of the substrate and then apply the printing or indicia to theopposite uncoated side thereof. Alternatively, the printing and adhesivecan be applied simultaneously on opposite sides of the substrate.Conventional coating, printing and other deposition techniques can beemployed for depositing the film plastic adhesive formulations,containing the discontinuously covered plasticizers. Of course, thecoating or deposition temperatures used should be below that at whichthe plasticizer and thermoplastic resinous adhesive would becomethermally activated.

One illustrative and exemplary procedure for prepar ing articles ofmanufacture (3) is as follows:

The roll of filler coated, thermoplastic adhesive coated wallpaper stockcan then be printed on the reverse (as yet uncoated) side byconventional wallpaper printing techniques (i.e., gravure printing)using conventional wallpaper printing inks, pigments, or dyes. Thisfinished prod uct can then be vinyl coated on the printed side and/orsubsequently embossed, without altering the basic functional propertiesof the thermoplastic adhesive coating.

It is also possible for the printing and/or the vinyl coating step to bedone prior to deposition of the filler and thermoplastic adhesivecoating. Alternately, the printing and the adhesive can be applied(simultaneously) on a single pass, eliminating rewind, on opposite sidesof the substrate, i.e., gravure to print and reverse roll to coat fillerat one station, and the same or another technique to apply thethermoplastic adhesive composition at another station.

As noted hereinabove, one of the major purposes of this is theproduction of prepasted Wallpaper and Wall coverings. The presentinvention, by the use of thermally activatable adhesives prepasted ontothe wall covering base stock, eliminates a large portion of the messyprob= lems associated with both conventional water-activated prepastedwall coverings and the even more problematic wet paste wallpaper. Thethermally activatable, prepasted wall coverings (3) can be appliedreadily by heat sealing the adhesive articles (3) to the Wall to becovered e.g., using an applicator which heats and presses the article(3) to the base with the heat being applied to the decorative side ofthe wallpaper. This is the same method of application to be used inafirxing the prepasted Wallpaper (3) to a wall, e.g., plaster wall, dryWall, wooden walls, etc. The applicator, e.g., a light weight hand ironor portable heated roller is of the heat regulated type so that the heatapplied to the paper (unpasted) side is of sufficient magnitude toactivate the adhesive, but insufiicient to cause thermal damage to thepaper base stock. Slight (hand) pressure is also applied via theapplicator, to assist in adhering the wallpaper or wall covering to 1 1the wall. Moderate pressures, e.g., ranging from 0.1 to 40 p.s.i. givesatisfactory applications.

A further embodiment of this invention resides in the production ofcomposite articles (7), such as prepapered wall panelling. An exemplaryand illustrative procedure for forming wallpaper panelling of prematcheddesigns on a suitable base is given hereinbelow. While the basespecifically mentioned below is conventional dry wall; the procedure isessentially the same regardless of the nature of the base material,e.g., plywood, composition board, Beaverboard, etc. Wallpaper stock orother decorative coated and/or laminate material is coated with thethermoplastic adhesive composition, printed, vinyl coated and/ orembossed as set forth above. This finished wallpaper is then adhered bythermal bonding, e.g., using applicators as noted above, to four foot byeight foot sheets of suitable conventional dry wall. The wallpaper mustbe prematched in such a manner that when the dry Wall is atfixed bysuitable methods (i.e., staples, nails, adhesive such as epoxy and othermethods) to studding or over other materials the wallpaper design willmatch in all cases and in all dimensions.

The invention will be illustrated in great detail by the examples whichfollow. In the examples below, all parts, percents, ratios andconcentrations are by weight unless otherwise indicated.

EXAMPLE I This example illustrates preparation of thermoplastic adhesivecompositions containing a mixture of thermoplastic resins with bothindividually covered plasticizer particles and a mixture of uncoveredplasticizers with the weight ratio between the individually coveredplasticizer and uncovered plasticizers being slightly less than 0.4321,,vis, the concentration of individually covered plasticizer solids was 30weight percent, based on total plasticizer present. In thesecompositions the ratio of covered plasticizer (core plasticizer) tocovering material ranged from 3 to 12:1.

The plasticizer to be covered, viz, a commercially available glycerolester of hydrogenated rosin marketed by Hercules Powder Company underthe trade designation Staybelite Ester No. was preground (single pass)in an ice crushing machine, along with Dry Ice, to reduce its size fromlarge chunks to a size where a fine grinding unit can subsequentlyhandle it, viz, to an average particle size of less than about 2,000microns.

Then 30 parts of the preground glycerol rosin ester plasticizer werepreslurried in 30 parts of water containing 0.45 part of a commerciallyavailable dispersing agent, Tamol 731 (Rohm and Haas Co.), which is asodium salt of polymeric carboxylic acid. This dispersion is then fed toan Attritor and finely ground to a particle size of less than 50microns, e.g., average diameter of approximately 20 microns.

A separate mixture of 60 parts of diphenyl phthalate and ten parts of acommercially available aryl sulfonamide-formaldehyde resin plasticizer,marketed by Monsanto Company under the trade designation Santolite MHP,(preground in the same manner as indicated above) was preslurried with1.05 parts of Tamol 731 and 70 parts of water. This mixture constitutesthe plasticizer which is to remain uncovered in the thermoplastic resinadhesive composition.

The glycerol ester slurry, containing the plasticizer solids to beindividually covered was then added to a suitable mixing tank, alongwith 27 parts of the higher melting polymeric latex covering material, acommercially available high molecular weight polyvinyl acetatehomopolymer aqueous emulsion containing approximately 55 weight percent(plus or minus 0.5 weight percent) of polyvinyl acetate solids (marketedunder the trade designation Polyco 2188 by Borden Chemical Company,Thermoplastics Division) and 210 parts of water. This mixture wasstirred from approximately 30 minutes.

Then 60 parts of anhydrous monosodium phosphate salt were added to themixture with stirring. One hour after the addition of the phosphatesalt, the formulation was heated to a temperature of 50 degreescentigrade and held at that temperature for three hours. The addition ofthe phosphate salt causes the polyvinyl acetate higher melting latexsolids to coalesce or accumulate about the dispersed solid plasticizerparticle cores thereby resulting in the individually covered plasticizersolids referred to previously herein. The heating for 3 hours at 50degrees centigrade is the ageing procedure referred to hereinabove, viz,the procedure whereby the adhesion between the recently depositedpolyvinyl acetate covering is enhanced with respect to the coreplasticizer material. The formulation containing the covered plasticizerparticles is then cooled to room temperature and stirred for a period of15 to 16 hours, viz, overnight.

Then the dispersion containing the thus covered plasticizer solids wasfiltered to a 40 to 50 percent solids filter cake, redispersed in freshwater and refiltered. This redispersion and refiltration procedure isrepeated twice to remove the residual phosphate salt from the coveredplasticizer solids. The weight percent solids remaining on the resultingfinal filter cake is approximately 67.2 percent. The final filter cakeis a loosely bound structure of covered glycerol rosin ester plasticizersolid cores having an average particle size of about 220 microns, withindividual bumpy coverings of polyvinyl acetate solids thereon. Theratio of covered (core) plasticizer to covering material wasapproximately 3:1.

The thermoplastic resin components of the adhesive, 54.5 parts of acommercial available polyvinyl acetate homopolymer emulsion, Polyco2188, and 127 parts of a commercially available copolymer emulsion of ananionic vinyl acetate-acrylate (marketed by the Borden Chemical Company,Thermoplastics Division, under the trade designation Polyco 2190) areplaced in a suitable mixing vessel to which is then added gradually withmixing the polyvinyl acetate latex covered glycerol rosin esterplasticizer solids. The previously finely ground mixture of diphenylphthalate and sulfonamide-formaldehyde resin plasticizers was then addedto the formulation tank, as a previously prepared dispersion, withstirring. Additional water was added to adjust the formulation to asolids concentration of 50 percent. The adhesive formulation, thusprepared, is now in a form suitable for coating using any of the abovedescribed procedures onto various substrates to enable said substratesto be heat sealed with moderate pressures to any desired base material,e.g., dry wall, plaster, wood, etc.

The above procedure was repeated except that instead of employing a 3:1weight ratio of core plasticizer to covering material; weight ratios of4:1, 8:1, and 12:1, respectively, were employed. The compositions wereotherwise the same as the 3:1 composition. Each of these compositions isuseful as an ambient temperature nontacky, blocking-resistant,heat-sealable thermoplastic adhesive, e.g., for prepasting wallpaper.

EXAMPLE II This example is similar to Example I except that the diphenylphthalate plasticizer solids are provided with the covering.

Separate aqueous dispersions of finely ground diphenyl phthalate and amixture of glycerol ester of hydrogenated rosin andsulfonamide-formaldehyde resin plasticizers were prepared in accordancewith the procedure of Example I. The diphenyl phthalate aqueousdispersion contained 60 parts of diphenyl phthalate, 60 parts of waterand 0.9 part of the Tamol 731 dispersing agent. The glycerol rosinester/sulfonamide-formaldehyde resin plasticizer mixture aqueousdispersion contained 30 parts of the glycerol rosin ester, 10 parts ofthe sulfonamideformaldehyde resin, parts of water and 0.6 part of theTamol 731 dispersing agent.

'The diphenyl phthalate dispersion was then provided with a covering ofpolyvinyl acetate homopolymer (Polyco 2188) using a 2:1 ratio ofdiphenyl phthalate core to the covering material. The individuallycovered plas- 't icizer solids were aged using the procedure of ExampleI.

The thermoplastic adhesive composition containing the individallycovered diphenyl phthalate solid plasticizer particles was thenformulated in accordance with the procedure of Example I, using thefollowing weight concentrations of the components. 1 part of total solidplasticizer (06 part of diphenyl phthalate, covered), 0.3 part ofglycerol ester of the hydrogenated rosin and 0.1 part of thesulfonamide-formaldehyde resin plasticizer, to one part of the sum offree polyvinyl acetate homopolymer, Polyco 2.188, and free polyvinylacetate copolymer, Polyco 2190, viz, total free latex. solids, in thesame weight concentration in which said latex materials are present inExample I. The final adhesive formulation contains 50 percent solids(adjusted by addition of water) as in Example I, and is useful as ablockingresistant prepaste coating for wallpaper.

EXAMPLE III This example is similar to Example I, with the exceptionthat the covered plasticizer is a mixture of diphenyl phthalate andsulfonamide-formaldehyde resin, Santolite MHP.

An a'qeuous dispersion of finely ground plasticizers containing amixture of 60 parts of diphenyl phthalate, parts of Santolite MHP, 70parts water, and 1.05 parts Tamol73l dispersing agent was prepared inthe manner specified in Example I. A separate aqueous dispersioncontaining 30 parts of finely ground glycerol ester of hydrogenatedrosin, Staybelite Ester No. 10, 30 parts of water and 0.45 part ofTamol-731 dspersing agent was also prepared under the Example Iprocedure.

The particulate mixture of diphenyl phthalate and thesulfonamide-formaldehyde resin plasticizer solids was provided withindividiual coverings of polyvinyl acetate homopolymer, Polyco 2188, andaged in the same manner as Example I. Then the thermoplastic resinadhesive was formulated according to the Example I procedure using thefollowing concentrations of the indicated components: 1 part total solidplasticizer (0.6 part of diphenyl phthalate, 0.3 part of said glycerolester hydrogenated rosin, and 0.1 part of sulfonamide-formaldehyde resinplasticizer) to one part of polyvinyl acetate homopolymer emulsion andpolyvinyl acetate copolymer emulsion as indicated in Example I. Thefinal adhesive formulation was adjusted by addition of water to contain50 weight percent solids.

Further preparations were conducted wherein the ratio of solidplasticizer to covering material in the discontinuously coveredplasticizer mixture was at 4:1 and 821. These adhesive formulations areuseful as blockingresistant prepaste coatings for wallpaper or otherwall covering materials, e.g., cloth coated with plasticized polyvinylchloride using dibutyl phthalate,,dioctyl phthalate di-Z-ethylhexylphthalate) as plasticizer. Such wall coverings are washable.

EXAMPLE IV This adhesive preparation procedure is essentially the sameas in Example I with the exception that the covered plasticizer is amixture of the glycerol ester of hydrogenated rosin and a sulfonamide-formaldehyde resin plasticizer.

An aqueous dispersion containing a finely ground mixture of 30 parts ofa glycerol ester of hydrogenated rosin, Staybelite Ester No. 10, 10parts of a sulfonamideformaldehyde resin plasticizer, Santolite MHP, 40parts of water and 06 part of a dispersing agent, Tamol-731, wasprepared in accordance with Example I. A separate aqueous dispersioncontaining 60 parts of finely ground diphenyl phthalate, 60 parts ofwater and 0.9 part disi4 persing agent, Tamol-73 l, was also prepared inaccordance with the Example I procedure.

Then the mixed plasticizer solids were provided with individualcov'erings of polyvinyl acetate homopolymer, Polyco 2188, employing aweight ratio of the mixed plasticizer core to the covering material of2:1 using the same procedure as in Example I. Subsequent to theformation of the covered plasticizer solids and the ageing of thecovering; the thermoplastic, heat sealing adhesive formulation wasprepared in accordance with the Example I procedure using the followingconcentration of the various components: 1 part of total solidplasticizer (0.6 part of diphenyl phthalate, 0.3 part of glycerol esterof hydrogenated rosin, and 0.1 part of sulfonamide-formaldehyde resinplasticizer) to one part of the total of polyvinyl acetate homopolymerplus polyvinyl acetate copolymer. The final formulation was adjusted bythe addition of water to contain '50 percent solids, in the manner notedin Example I. This adhesive formulation is likewise useful as ablocking-resistant prepaste coating for wallpaper or other wall coveringmaterials.

EXAMPLE V This example illustrates the enhanced resistance to blockingachieved by the thermoplastic adhesives of the present invention versuscomparable formulations which contain the same components but whereinthe plasticizer solids are not provided with individual covering.

Adhesive formulations having the below tabulated compositionalcomponents in the below indicated weight proportions were preparedessentially in accordance with the procedure indicated in Example I.Some formulations contained free (uncovered) plasticizer(s), viz, in thecontrol runs the plasticizer(s) are totally uncovered, and for thesecontrols, the covering procedure was by-passed, of course.

These adhesives were then applied to a bond paper substrate having aweight of approximately 41 pounds per 3000 sq. ft. ream. The adhesivecoatings were applied by the following procedure: The sheet to be coatedis taped to a coating stage. A small amount (approximately 20 cc.) ofadhesive is applied to the paper and the coating is drawn down mostusually using a number 30 Meyer rod to achieve a coating weight of mostusually 1711 pounds per 3000 sq. ft. ream of active adhesive, e.g.,solid thermoplastic adhesive film.

The coated substrates were then subjected to adhesive activation andblocking tests. The adhesvie activation tests We're conducted by holdingan adhesive-coated strip of forty-one pound per 3000 ft. ream bond paperagainst an uncoated strip of the same paper with the heat being appliedby placing a heated iron, maintained at 95 degrees centigrade for fiveseconds, on the uncoated side of the adhesive-coated paper sheet. Theblocking tests were conducted at room temperature (68 F.), F., and F. inaccordance with ASTM D1146-53 (1965). In reporting the blocking testresults, the terminology of ASTM D1l46-53 (196 5) has been employed. Theterms used are defined here for ready reference. Second Degree Blockingmeans an adherence of such extent that when the surfaces under test areparted one surface or the other will be found to be damaged. FirstDegree Blocking means an adherence between the surfaces under test ofsuch extent that when the specimen is lifted the lower specimen willcling thereto, but may be parted with no evidence of damage to eithersurface. Free means absence of both second and first degree blocking.

In Table 1 below, a Yes entry means that the specimen tested exhibited aSecond Degree block; a No entry means that the specimen tested did notexhibit a Second Degree block, but did show a First Degree block; and aFree entry means no blocking, whatsover. Adhesives resulting in FirstDegree block are considered acceptable for most purposes including useon wallpaper. Adhesives resulting in Second Degree block are 0on sideredunacceptable for most purposes including use on wallpaper. Adhesivesresulting in Free of all blocking are considered acceptable for allpurposes insofar as resistance to blocking is concerned.

the particular substrate employed. This will be illustrated below usingone heat-sensitive substrate, viz, paper.

Thermoplastic, heat-sealing adhesives were prepared in accordance withthe Example I procedure and con- TABLE 1 Blocking at Ratio of Thermalroom temp. Blocking Blocking Total Ratio total covered activation (68F.) and at 105 F. at 140 F. plasti- Polyco 2188 plastiseconds 19.5.1. (1p.s.i.) (1 p.s.i.) cizer to total Ilastlcizcr(s) at 95 C., concen-Polyco 2100 covered 203 F.) AA 1 PA 2 AA 1 PA 2 AA 1 PA 2 nation 3 :85None No Yes... Yes... 50.0 S No.... Yes-.. Yes... 46.3 No.-.. Yes-..50.0 Free Yes. 51. 3 No. Yes... 50.0 No.... Yes... 58.9 No.... Yes...46. 3 No.... Yes... 49. 4 Yes. 40. 1 Yes. 50. 0 Yes. 64. 5 Yes-.. 55. 5Yes... 48. 2 Yes-.. 50. 0 Yes. 46. 3 Yes... 50.0 Yes... 45. 0 Yes. 46. 3

None Y DPP; SE-lO and MHP (V12, all).

Yes... No.... No.... Yes... No.... Yes-..

1 AA=Adhesive to adhesive.

2 PA=Paper to adhesive.

3 Weight percent, based on total latex plus total plasticizer. 4 Both.

As will be noted from Table 1 above, the thermoplastic, heat-scalableadhesives containing individually covered plasticizer in accordance withthis invention alford enhanced resistance to blocking over comparableadhesives but where the plasticizer is totally uncovered. Thus, theblocking resistance in each of control Runs 1, 3, 5, 10, 14, 16, 19 and21 is enhanced by use of the present invention. The improvements inblocking resistance afforded by the present invention, without loss ofthermal activation and adhesion properties, are readily apparent. Itwill also be noted that these improvements are general, viz, they areattainable over a wide range of: thermoplastic resin compositions,ratios of plasticizer to covering, concentration of total plasticizerwhich is provided with covering; total plasticizer concentration, etc.

EXAMPLE VI Each thermoplastic resin (or combination of resins) will haveits own substrate-oriented heat sealing temperatures which should beobserved in order to achieve satisfactory thermal activation withoutdeleteriously affecting a given substrate material. The same basicadhesive, viz, having the same overall compositional ratio of highermelting polymer to lower melting polymer can thus be tailor-made to heatseal at different temperatures, depending on the particular substrate towhich it is applied, by controlling the concentration of higher meltingpolymer which is present as covering material. This example illustratesthe effect on thermal activation temperatures which the concentration ofthe higher melting polymer covering material has.

Hence, in order to avoid thermal damage to a given substrate material,its maximum heat sealing temperature should not be exceeded. That is notto say that heating to the thermal activation temperature(s) causespyrolitic damage to the thermoplastic adhesive, however; but merely thateach substrate limits the maximum thermal acti vation (heat-sealing)temperature which can be used with the adhesive coated thereon.Therefore, the thermal activation temperature(s) of the adhesive can becontrolled by limiting the concentration of higher melting coveringpolymer to a concentration range in which it secures adequate resistanceto blocking yet can be thermally activated at a low enough temperatureto avoid thermal damage to taining the below tabulated concentrations oftotal plasticizer, at least a portion of which was provided with apolyvinyl acetate homopolymer (Polyco 2188) discontinuous covering as inExample I. The covering was aged and the adhesives were formulatedcontaining the polyvinyl acetate homopolymer and polyvinyl acetatecopolymer according to Example I above.

These adhesives were then coated onto a bond paper substrate having aweight of approximately 41 pounds per 3000 sq. ft. ream. Then thermalactivation and blocking tests were conducted as in Example V. Thepertinent experimental data are summarized in Table 2.

In each of the below runs, 50 weight percent of total plasticizer isdiphenyl phthalate, 30 weight percent is a glycerol ester ofhydrogenated rosin and 10 weight percent is a sulfonarnide-formaldehyderesin.

In Runs 3, 7 and 9, 60 weight percent of total plasticizer wasindividually covered, viz, the diphenyl phthalate. In Runs 1, 2, 4 and6, 40 weight percent of total plasticizer was covered, viz, a mixture ofglycerol ester of hydrogenated rosin (Staybelite Ester No. 10) and arylsulfonamide-formaldehyde resin plasticizer (Santolite MHP). In Runs 5, 8and 10, weight percent (viz, all) of the plasticizer is covered, viz,two types of covered plasticizers, one being a mixture of glycerol esterof hydrogenated rosin with sulfonamide-formaldehyde resin and the otherbeing covered diphenyl phthalate.

As indicated from the data in Table 2, unsatisfactory heat sealing(thermal activation) results from'too high a concentration of coveringmaterial when the substrate material dictates a maximum practicaltemperature for heat sealing. Usually in order to avoid heat damage tothe paper, the thermoplastic adhesive should not require thermalactivation temperatures substantially in excess of about C. (312 F.).Thus, for such selected thermoplastic resinous adhesives, theconcentration of covering polymer should usually be less than about 40percent to avoid thermal damage to the paper substrate.

It should be noted, however, that covering polymer concentrations of 40percent and higher do not adversely affect resistance to blocking aswill be noted from the blocking results for Runs 8-10. Moreover, thethermoplastic adhesives of Runs 8-10 did activate well at 150 C. (302F.) in five seconds without causing thermal damage to the adhesive.Hence, higher concentrations of covering material can be used inconjunction with substrates having greater resistance to heat withoutlosing either proper heat sealing or enhanced resistance to blocking.While the adhesive formulations of Runs 8 to 11 are suitable for use onpaper substrates even though the covering latex concentration exceeds 40percent; this is because paper can Withstand the 150 C. thermalactivation temperature. On the other hand, with substrate materialswhich are more sensitive to heat, e.g., vinyl plastic substrates,adhesives should be used which can be thermally activated attemperatures not substantially in excess of about 95 C. In such casesthe concentration of covering latex should usually be less than about 40percent.

EXAMPLE VII Use of heat, rather than salt to form covering Thirty partsof preground (as in Example I) glycerol ester of hydrogenated rosin,Staybelite Ester No. 10, were preslurried in 30 parts of watercontaining 0.45 part of Tamol 371. This dispersion is then fed into anAttritor and finely ground to a particle size of less than 50 microns,e.g., average diameter of approximately 20 microns.

The glycerol ester slurry, containing the plasticizer particles providedwith individual coverings, was then added to a suitable mixing tankalong with 4.55 parts of the higher melting polymeric latex coveringmaterial,

are added to a suitable vessel equipped with a stirrer. To this emulsionblend is added with stirring 65 parts of an aqueous SE dispersion whichcontains 50 percent solids (30 parts SE10) which have been individuallycovered with 2.5 parts Borden Polyco 2188 partcles (12:1 phase ratio)via either the salt coagulation procedure outlined in Example I or bythe heat coagulation method outline in Example VII. Also added withstirring are 140 parts of a DPP-MHP aqueous dispersion which contains 1050 percent solids (60 parts DPP, 10 parts MHP, and a very small amountof Tamol-73l dispersing agent). 18.5 parts of water are then added toadjust the total solids of the formulation to 50 percent. Thisformulation is referred to as A.

The same formulation as above was prepared again; however, neither theSE10 nor any of the other components were provided with a covering ofhigher melting Polyco 2188 homopolymer particles. This formulation isreferred to as B.

Both of these formulations are similarly coated to give appr0ximatelyequivalent coating weight on both Mylar, a commercially availablepolyester, viz, polyethylene glycol terephthalate, and Tyvek, acommercially available rubber treated paper product with high 25strength. ASTM blocking tests were run on the thus adhesively coatedMylar sheets to determine both adhesive to adhesive and adhesive toMylar (AM) blocking.

TABLE 2 Blocking Percent Parts at room covering Polyco temperatureBlocking Blocking latex, 2188 as Parts Parts Thermal (68 F.), at 105 F.at 140 F. based on indi- "Polyco Polyco activation 10 p.s.i. (1 p.s.i.)(1 p.s.i.)

tot vidual 2188 2190 (5 seconds latex covering free (all free) at 95 0.)AA PA AA PA AA PA 18.0 8.8 16. 0 24.0 Yes No No No No Yes Yes. 21.1 5.0None..- 18.75 Yes No- No Yes No Yes- No. 28.6 7.5 do 18.75 Yes No No YesNo Yes-.. Yes. 28.6 5.0 ...do 12.5 Yes No No Yes... No. Yes-.- Yes. 35.421.9 16. 0 24.0 Yes No- No Yes- No- Yes-.. No. 36.4 5.0 None--- 8.75 YesNo 0- Yes. No Yes-.- Yes 37.5 7.5 do 12.5 Yes No No Yes-.. No Yes-.. Yes40.0 12.5 do 18.75 Slight-.." No No Yes-.- No Yes Yes. 46.1 7.5 do--8.75 do No No Yes-.. No Yes..- Yes. 59.2 12.5 do 8.75 do No No Yes... NoYes-.. Yes.

a commercially available polyvinyl acetate homopolymer aqueous emulsioncontaining 55 weight percent of polyvinyl acetate solids and 98 parts ofwater. This mixture was stirred for approximately minutes.

The formulation is then heated to a temperature of C. and held at thattemperature for 3 hours. The heating causes the polyvinyl acetate highermelting polymeric latex solids to coalesce or accumulate about thedispersed solid plasticizer particle cores thereby resulting in theindividual covering referred to previously herein. The heating also isthe ageing procedure referred to hereinabove. The formulation containingthe individually covered plasticizer particles is then cooled to roomtemperature and stirred for a period of 15 to 16 hours, viz, overnight.This dispersion is then formulated, after filtering as in Example I,with the DPP-MHP dispersion and the blend of Polyco 2188 and Polyco 2190referred to in Example I.

EXAMPLE VIII This example illustrates the use of the blocking-resistantadhesives of the present invention on polyester and rubber surfacedpaper substrates, respectively, on a comparative basis versusessentially the same adhesive but employing wholly uncoveredplasticizers.

54.5 parts of percent Borden Polyco 2188 emulsion and 127 parts of 55percent Borden Polyco 2190 emulsion The blocking test results areindicated below in Table 3.

ASTM Peel Strength tests were run at 180 F. using formulations A and B,respectively, to :bond Mylar" to Mylar and Mylar to Tyvek. The bondstrength test results reveal that no loss of bond strength accom paniesthe use of the adhesive A containing the covered plasticizer; yet asnoted in Table 3, better blocking-resistance is attained.

What is claimed is:

1. Randomly shaped, particulate, blocking-resistant plasticizer solidseach comprised of a normally cold flowable, thermally activatable,water-insoluble, tackifying plasticizer core having an about 0.02 toabout 20 microns thick, substantially continuous, solid-retaining,

comparatively hard individual covering comprised of polymeric materialhaving a melting range the threshold temperature of which is higher thanthat of the thermal activation temperature of said tackifyingplasticizer core, said individually covered plasticizer solidscharacterized by being nontacky at ambient temperatures due to theinhibition of the cold flowing tendency provided by said covering.

2. Blocking-resistant plasticizer solids as in claim 1 wherein thepredominant shape of said randomly shaped solids is generally spherical.

3. Blocking-resistant plasticizer solids as in claim 1 wherein saidindividual covering contains bumpy projections of general rounded shape.

4. Blocking-resistant plasticizer solids as in claim 1 wherein theweight ratio of plasticizer core to higher melting covering materialranges from about 1.5 t 20: 1.

5. Blocking-resistant plastitizer solids as in claim 3 wherein saidbumpy projections range in size from about 0.01 to about 1 micron.

6. Blocking-resistant plasticizer solids as in claim 1 wherein theplasticizer core is comprised of a mixture of plasticizers.

7. Blocking-resistant plasticizer solids as in claim 1 wherein saidplasticizer core has a particle size less than about 50 microns.

8. A blocking-resistant, heat-sealable, thermoplastic adhesivecomposition comprising thermoplastic resin and from about 7 to about 25weight percent, based on total thermoplastic adhesive includingplasticizers, of individually covered; blocking-resistant plasticizersolids as in claim 1 uniformly distributed therein.

9. A blocking-resistant, heat-scalable, thermoplastic adhesivecomposition as in claim 8 which includes uncovered plasticizersufficient to constitute a total plasti cizer concentration up to about33.3 weight percent, based on total adhesive including plasticizers.

10. A blocking-resistant, heat-scalable, thermoplastic adhesivecomposition as in claim 8 wherein the concentration of higher meltingpolymer including that providing said covering ranges from about 0.3 toabout 18 weight percent, based on total adhesive including plasticizers.

11. A blocking-resistant, heat-sealable article comprising a substratehaving secured thereto on one side a thermoplastic adhesive compositionwhich is resistant to blocking at ambient temperatures comprising thermoplastic resin and uniformly distributed therein from about 7 to about 25weight percent, based on total thermoplastic adhesive includingplasticizers, of individually covered, blocking-resistant particulateplasticizer solids each comprised of a normally cold flowable, thermallyactivatable, water-insoluble, tackifying plasticizer core of particlesize less than about 50 microns having an about 0.02 to about 20 micronsthick, substantially continuous, solid-retaining, comparatively hard,individual covering comprised of water-insoluble polymeric materialhaving a melting range the threshold temperature of which is higher thanthat of the thermal activation temperature of said plasticizer core toenable said plasticizer to egress upon thermal activation of saidadhesive at thermal activation temperatures, said covering restrictingaccess of said core plasticizer to said resin at temperatures belowthermal activation temperatures thereby inhibiting the cold flowingtendency of said core plasticizer and enhancing the blocking-resistanceof said adhesive.

12. An article as in claim 11 wherein the substrate is paper.

13. An article as in claim 12 wherein said paper has indicia on thenonadhesive side and said paper substrate is thermally strippable from abase due to said adhesive.

14. An article as in claim 11 wherein the substrate is washable wallcovering material.

15. An article as in claim 11 wherein the substrate is metal foil.

16. An article as in claim 11 wherein the substrate is plastic.

17. An article as in claim 12 wherein the paper substrate is wallpaperranging in weight from about 40 to about 90 pounds per 3000 ft. ream andsaid adhesive is present in a concentration of from about 1 to aboutpounds per ream.

18. A process for preparing blocking-resistant plasticizer solidscomprising dispersing solid, water-insoluble, plasticizer core particleshaving a size less than about 50 microns in an aqueous latex ofcomparatively hard, higher melting, water-insoluble, particulatepolymeric material having an average particle size ranging from about0.5 to about 2 microns; coalescing the latex particles about saidplasticizer cores to provide individual, higher melting, polymeric latexcoverings for said plasticizer cores; and heating said coveredplasticizer cores at a temperature ranging from about 40 C. to a maximumtemperature below that at which said plasticizer core melts to enhanceadhesion between said covering and said core thereby providing each saidcore particle with a substantially continuous, solid-retaining covering.

19. A process of making heat activable-prepasted wall covering which isresistant to blocking at ambient temperatures comprising depositing anaqueous dispersion containing from about 30 to about weight percentadhesive solids of the adhesive composition of claim 8 on a wallcovering substrate in a concentration of from about 1 to about 50 poundsof adhesive (dry basis) per 300 ft. ream, and removing excess water.

20. A process as in claim 19 wherein said wall covering substrate iswallpaper.

21. A process as in claim 19 wherein said substrate is a washable wallcovering comprised of cloth coated on its viewed side with flexibleWater-resistant plastic material.

22. Prewall covering decorative panelling comprised of a base panelhaving decorative wall covering material secured thereto by the adhesiveof claim 8 thermally activated.

23. Decorative panelling as in claim 22 wherein said decorative wallcovering is wallpaper.

24. Decorative panelling as in claim 22 wherein said decorative wallcovering is a washable wall covering comprised of cloth coated on itsviewed side with flexible, water-resistant plastic material.

References Cited UNITED STATES PATENTS 10/1952 McGafiin 26034.2 3/1963Craig 1l'727 WILLIAM J. VAN BALEN, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 558,418 Dated January 26, 1971 Inventor(s) Erland C. Porter, Jr. and Hans F.Huber It is certified that error appears in the above-identified paterand that said Letters Patent are hereby corrected as shown below:

Column 2, line 1, after "threshold" insert line 19, 'adhesive", secondoccurrence, should be plural. Column 3, line 19, "When" should be--While--. Column 4, line 44, "polphenyls" should be --polyphenyls--;line 58, "glycol monostearate" should be --glycerol monostearate".Column 11, line 75, "from" should be --for-. Column 13, line 59, before"di" insert Column 14, line 48, "adhesvie" should be --adhesive--. Claim4, line 3, "0t" should be --to--. Claim 19, line 8, "300" should be---3000--.

Signed and sealed this 18th day of May 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, Attesting OfficerCommissioner of Peten

